TOOL LIFE RELIABILITY OF INDEXABLE CUTTING INSERTS

Transcription

1 TECHNOLOGICAL ENGINEERING Volume IX, umber 2/2012 ISSN DOI: /tee TOOL LIFE RELIABILITY OF INDEXABLE CUTTING INSERTS Article history: Received 2 september 2012 Accepted 17 ovember 2012 Available olie 11 december 2012 Adam Jaásek, MSc. Robert Čep, assoc. prof. Ph.D. MSc. Leka Čepová, PhD. MSc. Jiří Kratochvíl, Ph.D. MSc. Vladimír Vrba, assoc. prof. Ph.D. MSc. Leka Petřkovská, Ph.D. MSc. Departmet of Machiig ad Assembly, Faculty of Mechaical Egieerig VŠB Techical Uiversity of Ostrava, Czech Republic Abstract This paper presets experimetal testig of the cuttig ability for idexable cuttig iserts. The mai goal will be to select a suitable test for determie the cuttig abilities of cuttig iserts. Nowadays all maufacturers wat to achieve lower cuttig forces so ca permit higher speeds ad feeds, without icreasig the risk of chippig. For evaluatig we had to desig such testig procedure that it would be possible to compare ad evaluate the cuttig ability of the selected cuttig iserts used for tests. I today s competitive global market, quality ad precisio is the most importat parameter. Tight toleraces ad urget deadlies are ormal. I the machie tool busiess, compaies must keep their cuttig edge, or your compay will lose its competitive edge. The cotact pheomea o the tool flak surface are of iterest because uderstadig them allows the explaatio of tool flak wear ad the formatio of surface itegrity of machied surfaces o workpieces. Normally, abrasio, adhesio, diffusio ad oxidatio types of cuttig tool wear are discussed i literature o metal cuttig. However, i the machiig of difficulttomachie materials ad i high speed machiig, plastic lowerig of the cuttig edge is the predomiat cause of premature tool failure. This is due to the plastic deformatio of the cuttig wedge (a part of the tool betwee the rake ad the flak cotact surfaces). [1] Keywords Machiig; Idexable Cuttig Isert; Cuttig Ability 1 Itroductio The developmet is so fast, ad the requiremets of the customer are still growig, is required to begi with the tests which are ot demadig o time ad are sufficietly accurate. Today the customer demads quality tools, reasoable price ad quick delivery time. Nowadays, the security margis are so tight, that eve our safety depeds o the quality of the materials that we use every day, so it is very importat to be able to maufacture parts at high level of productivity or quality. Parallel to the materials developmet there was also the improvemet of tool materials, especially ceramic tool materials. The preset ivetio relates to a high performace coated cuttig tool isert particularly useful for turig ad tough hardeed steels i the area from fiishig to roughig i wet ad dry coditios at high cuttig speed, havig the ability to withstad high temperatures. 2 Test Descriptio Thaks to a large umber of tested iserts was better to choose the direct shortterm cuttig test. The cuttig ability test will be doe by the frot test. It is ecessary to select a sufficietly large diameter of the machied material for the iserts with a higher cuttig ability ot to cut away the whole material frot ad ot be sufficietly wor out uder the selected cuttig parameters at the same time. This way it would ot be possible to measure requested diameters o the tested frot of a machied material. Figure Machied Material Scheme for Direct Shortterm Test It is advisable to select a higher quality of the machied material with worse machiability for more impartial testig [4, 6]. We have selected the 42CrMo4 material. This is a chromemolybdeum steel suitable for beig tempered i oil. It has icreased resistivity agaist drawig ad ca be used i icreased temperature up to approx. 500 C. Alloyed heat treatable steel with a typical tesile stregth of N/mm². For automotive ad aircraft compoets with high toughess as axle jourals, gears, tyres, etc. Table 1 Chemical Compositio of 42CrMo4 Material C M Si Cr Ni Mo P S TECHNOLOGICAL ENGINEERING, Volume IX, umber 2/2012, ISSN Uautheticated Dowload Date 2/7/18 3:47 PM

2 2.2 Idexable Cuttig Isert We selected eleve uptodate types of exchageable cuttig iserts from five maufacturers as the tested material (see i Table 2). Each test was carried out three times so we could reach the accuracy ad precisio of each test. Table 2 Tested Cuttig Materials Item Maufacturer Markig Material 1. Pramet CCMT E Pramet CNMG E Pramet CCMT E Pramet CNMG E Pramet CCMT E Pramet CCGT ER Sadvik CCMT Mitsubishi CCMT NX Mitsubishi CCMT UC Widia CCMT TN Boehlerit CCMT LC225T Table 3 Used Cuttig Parameters Revolutios [rpm] Feed f Cuttig depth ap Chose Turig Lathe With regard to the experimet requiremets we selected the turig lathe SU 50A for the testig with the maximal turig diameter above the machie bed 500 mm, maximal turig legth mm ad the maximum revolutios rpm, what is sufficiet for the test [2]. It had to be ecessary to provide the maximum rigidity for the machie ad testig tools as well. 2.3 Cuttig Coditio The cuttig parameters, i.e., feed ad cut depth is idetical for each test. Oly revolutios will be chage. The cuttig depth ap must be selected ot to be larger or eve to the biggest radius of the tip of the selected idexable cuttig isert. This would cause faster toolwear of the isert ad oobjectivity of the whole testig. Figure Measured Values Measured ad Average Values with Descriptio Testig Used SU 50A Turig Lathe Table 4 Measuremet umber Ø D1 Item Maufacturer Markig Isert Material 1. Pramet CCMT E φd Pramet CNMG EM 6610 φd Pramet CCMT E φd Pramet CNMG EM 6640 φd Pramet CCMT E φd Pramet CCGT ERSI 8030 φd Sadvik CCMT MM 2025 φd Mitsubishi CCMT NX2525 φd Mitsubishi CCMT UC6010 φd Widia CCMT TN 7025 φd Boehlerit CCMT BSM LC225K φd Table 5 Table of Measured ad Calculated Values Item Maufacturer Markig Isert Material vc1 [m/mi] vc2 [m/mi] m [] CT [] T1 [mi] Ø D2 T2 [mi] 1. Pramet CCMT E ,4 654,2 1,2 3,15x10 3 1,72 1,29 2. Pramet CNMG E ,4 602,4 1,5 1,67x10 4 1,53 1,09 3. Pramet CCMT E ,8 471,0 2,2 3,97x10 5 0,94 0,57 4. Pramet CNMG E ,5 394,2 1,8 2,4x10 4 0,48 0,27 5. Pramet CCMT E ,3 401,3 2,0 1,06x10 5 0,55 0,30 6. Pramet CCGT ER ,0 361,3 1,6 6,6x10 3 0,28 0,14 7. Sadvik CCMT ,2 403,7 2,3 4,06x10 5 0,59 0,31 8. Mitsubishi CCMT NX ,6 431,4 2,9 1,54x10 7 0,79 0,42 9. Mitsubishi CCMT UC ,5 461,1 4,9 3,58x ,07 0, Mauf 10 CCMT Qt ,8 436,2 2,7 6,41x10 6 0,80 0, Mauf 11 CCMT Qt ,3 431,0 2,4 1,25x10 6 0,75 0,42 TECHNOLOGICAL ENGINEERING, Volume IX, umber 2/2012, ISSN Uautheticated Dowload Date 2/7/18 3:47 PM

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4 2.6 Compariso of Measured Values If we wat to compare the cuttig ability of isert, it is ecessary to select some parameter. I case of this experimet it would be the most suitable to select the time T. This is the time of tool life for oe edge uder selected cuttig coditios. Amog the iserts with the best cuttig ability are umbers 1 ad 2 from Pramet maufacturer. Both iserts are made from 6610 material. With regard to the chip creatio with these iserts we could say that the umber 1 has much more better chip creatio, which is very importat parameter durig machiig. The item umber 4 has worse tool life ad also zero back agle. The suitable isert for semirough cuttig to fiishig would be the isert umber 9 from Mitsubishi maufacturer. Oe of differet causes of cuttig ability of the iserts (6610 ad 6640 coated materials) from Pramet [7] is also differet coatig material. For 6640 material it is a thi coat layer with TiCN support layer applied by the MTCVD method ad for 6610 material it is a thick coatig with the Al2O3 support layer applied by the MTCVD method. The fial results for the whole test, ad their evaluatio were very surprisig. Tests showed that betwee the best ad worst cuttig ability isert that is more tha 80% worse tha the umber 1 lies the umber 6 with a atypical shape ad 8030 material. [3] Specially coated iserts have elevated performace sice their itroductio, ad cotiue to do so. Ad, they show further potetial for future developmet. The toolmaterial sciece of coated iserts is very much a hightech area today. 2.7 Evaluatio of Experimet Cuttig Parameters Recommeded by the Maufacturers Isert vc v15 Item Maufacturer Markig Material [m/mi] [m/mi] f ap 1. Pramet CCMT E ,20,6 1,08,0 2. Pramet CNMG EM ,150,6 0,86,0 3. Pramet CCMT E ,20,6 1,06,0 4. Pramet CNMG EM ,170,4 1,25,0 5. Pramet CCMT E ,20,6 1,08,0 6. Pramet CCGT ERSI ,20,44 1,04,0 7. Sadvik CCMT MM ,090,27 0,33,6 8. Mitsubishi CCMT NX ,050,2 0,52,0 9. Mitsubishi CCMT UC ,10,25 0,53,0 10. Widia CCMT TN ,120,4 0,75,0 11. Boehlerit CCMT FM LC225T ,10,6 0,86,0 Table 6 The values v15 are cuttig speeds for 15 miutes of toollife, deducted from the graphs No The toollife should be 15 miutes at the cuttig speed. If we compare the cuttig speed vc, which are recommeded by maufacturer, you ca otice sigificat differeces. The maufacturer specifies the coditios for material with 180HB hardess ad grade of machiability 14b. This is the mai differece i cuttig speeds because the material used for our experimet has a 280 HB hardess ad grade of machiability 10b. Geerally, the sitered carbide iserts are used for more difficult cuttig material at cuttig speed approximately 100 m/mi. TECHNOLOGICAL ENGINEERING, Volume IX, umber 2/2012, ISSN Uautheticated Dowload Date 2/7/18 3:47 PM

5 2.8 Techical ad Ecoomical Evaluatio Figure 3 Ecoomical Compariso of Differet Iserts We ca otice two types of iserts, which are sigificatly more expesive. They are the items 6 ad 7, from the Pramet ad Sadvik. Item 6 has the lowest cuttig power ad also has the highest price. It was suggested ot to use a isert for material with worse machiability ad ot to use at higher cuttig speeds. Also Sadvik isert does ot have a satisfactory toollife accordig to price parameter. This isert should be rather lookig for apportuities i the stailess steel machiig as recommeded by the maufacturer. The cost of others iserts are ot too differet. The best price appears items 1 ad 2 due to cuttig power. 3 CONCLUSION FOR EXPERIMENT The developmet of the cuttig tools has a held a key positio i this time. The techology of the machiig processes has bee improved cotributios from all the braches of idustry area with a iterest i machiig. For better cuttig ability compariso the best would be to test o differet quality materials ad chage feed speeds or chip depths. The aim was to select idexable cuttig isert for use at semirough ad fiishig operatio ad compare their cuttig power, compile depedecy of toollife o cuttig speed. These tests showed that the best cuttig ability is performed by two Pramet iserts, made of the 6610 material ad marked as CCMT E48 ad CNMG EM. Aother advatage of Pramet iserts is also their low purchase price. The 5.199, CZK was calculated as cost of iserts for the experimet. The 4.350, CZK was cost of material. The total cost of the experimet, without eergy ad labor, have bee established o 9.545, CZK. The measuremet of toolwear o the cuttig edge has ot a larger meaig ad the measuremet of the size will ot show ay detailed iformatio at this experimet. Before startig our ext project it would be a better to compare a cuttig power o the various grades of steel or chage the feed rate or depth of the chip. Literature [1] P. ASTAKHOV, Viktor. The assessmet of cuttig tool wear. Iteratioal Joural of Machie Tools & Maufacture. 2004, č. 44. [2] NESLUSAN M, et. al. Experimetali metody v triskovem obrabei. Zilia: EDIS Zilia, ISBN [3] CERNAK. Toollife Tests of Iserts. Ostrava: Departmet of Machiig ad Assembly. Faculty of Mechaical Egieerig, VŠB Techical Uiversity Ostrava, 2007, Graduatio thesis, head: Ig. Robert Čep, Ph.D., MSc. [4] CEP, R.; NESLUSAN, M.; BARISIS, B. Chip Formatio Aalysis Durig Hard Turig. Strojarstvo, 2008, vol 50, No. 6, p ISSN [5] VARGA G., BALAJTI Z., DUDAS I. Advatages of the CCD Camera Measuremets for Profile ad Wear of Cuttig Tools. Joural of Physics: Coferece Series 13, 2005, pp.: , IoP, Istitute of Physics Publishig, Bristol ad Philadelphia, ISSN [6] HATALA, M. Simulacie techologickych procesov. 1. ed. Prešov: FVT TU, p. ISBN [7] O. BILÍK, Obráběí II 1. díl Fyzikálě mechaické zákoitosti procesu obráběí, Ostrava ISBN X. [8] JANÁSEK, A ČEP, R. ČEPOVÁ, L: Selected parameters measuremet of surface itegrity after ceramic tools machiig. I Techologické ižiierstvo, ISSN , 2011, vol. 8, o., 2. ISSN TECHNOLOGICAL ENGINEERING, Volume IX, umber 2/2012, ISSN Uautheticated Dowload Date 2/7/18 3:47 PM